IEEE 802.15.1 (a.k.a. Bluetooth)IEEE 802.15.1 (a.k.a. Bluetooth)

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Bluetooth:

• King Harold Blatand, or Bluetooth, a Viking and King of Denmark 940-981, united Denmark & Norway

• 1994 – Ericsson study on a wireless technology to link mobile phones and accessories

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Bluetooth working group history

• February 1998: The Bluetooth SIG is formed– promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba

• May 1998: Public announcement of the Bluetooth SIG

• July 1999: 1.0A spec (>1,500 pages) is published• December 1999: ver. 1.0B is released• December 1999: The promoter group increases to 9

– 3Com, Lucent, Microsoft, Motorola

• March 2001: ver. 1.1 is released• Aug 2001: There are 2,491+ adopter companies• Nov. 2003: ver. 1.2 is released• Nov. 2004: ver. 2.0 is released

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Bluetooth positioning

• Bluetooth:– Wireless voice and data for mobile devices

• IrDA:– Wirelss data cable replacement for devices in line of sight

• HomeRF:– Networking mobile data and voice devices to a PC anywhere in the

home

• IEEE 802.11 and Hiperlan 2:– Wireless enterprise networking in the office

• DECT:– Wireless voice at home and in the office

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Bluetooth positioning

Coverage

Ban

dwid

th

WLAN

BluetoothGSM

DECTWLANIrDA

GPRSUMTS

GPRS

GSMDectBlu

etoo

thIR

UMTS

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Bluetooth positioning

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Usage Models

• Headset – hands free cell phone (road, office, car)

• 3 in 1 Phone – intercom (no charge), portable phone (fixed line charge), cellular – Office-->LAN/PSTN Home-->PSTN

• Internet Bridge – Network access point, for mobile internet browsing

• Automatic Synchronizer – Background syncs between PC & PDA, Phone & PC, etc.

• Instant Postcard – digital camera send to cell phone

• Interactive Conference – Exchange business cards & data in meetings

• Wireless Workplace – Peripherals connect to your PC or LAN without wires

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Core Bluetooth Products

• Notebook PCs & desktop computers

• Printers• PDAs• Other handheld devices• Cell phones• Wireless periperals:

– Headsets– Cameras

• Access Points

• CD Player• TV/VCR/DVD• Telephone Answering

Devices• Cordless Phones• Cars

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Other Products…

• 2004 Toyota Prius – hands free calls• Toshiba Washer & Dryer – downloads the

washer/dryer software for new clothes!• Nokia N-gage • Digital Pulse Oximetry System

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Future Usage Scenarios

• Home Automation• Home Entertainment/Games• Electronic Commerce/M-Commerce• Industrial Control• Surveillance• Access Control• Location Based Services• Current Trials: Shopping Malls, Train Stations• ……

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Key Success Factors

• Interoperability (assured by BQB)• Mass Production at Low Cost• Ease of Use• End User Experience

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Bluetooth Qualification Body (BQB)

• A person authorized to provide qualification services for products

• Bluetooth Qualification Test Facility (BQTF)• Preparation – Testing – Assessment & Listing – Qualified

Products List (QPL) • Stats (as of 02/01/04):

– Qualified Products: 1368– BQBs Worldwide: 35– BQTFs Worldwide: 25– Only 4 of each in US

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Bluetooth Profiles

• Profiles implement usage models• Profiles will use 1 or more protocols• Qualification based on set of profiles provided

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Profiles & Services

• An application that provides a capability to another device, e.g. printing, LAN Access, synchronization, etc.

• Bluetooth profiles define core services• Programmers can write new services

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Example...

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Baseband

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Bluetooth Technical Features

• 2.4 GHz ISM Open Band– Globally free available frequency– 79 MHz of spectrum = 79 channels– Frequency Hopping & Time Division Duplex (1600 hops/second)

• 10-100 Meter Range– Class I – 100 meter (300 feet)– Class II – 20 meter (60 feet)– Class III – 10 meter (30 feet)

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Frequency Hopping among Piconets

• Typically, FH scheme uses carriers spacing of 1 MHz with up to 79 different frequencies.

• f = 2402 + k ; k = 0…78

• So, with FH, there are 79 logical channels (theoretically).– When two piconets choose the same 1MHz-band, collision occurs.

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Frequency hopping

Time

Frequency

0

78

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Frequency Hopping Sequences

• Each time, the FH kernel selects a segment of 64 adjacent channels, and then hops to 32 of them without repetition in a random order

• Next, a different 32-hop sequence is chosen from another segment of 64 adjacent channels

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Interference

• Frequency hopping

• Short range

• Power control

• FEC and ARQN

• Short packets and fast acknowledgements

• Other equipment in ISM band e.g. WLAN, micro-wave

oven, etc.

• Adaptive Frequency Hopping (AFH) is proposed in

IEEE 802.15.1.

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Bluetooth Link types

• Synchronous Connection Oriented (SCO)– Circuit switched typically used for voice

– Symmetric, synchronous service

– Slot reservation at fixed intervals

– Point-to-point

• Asynchronous Connectionless Link (ACL)– Packet switched

– Symmetric or asymmetric, asynchronous service

– Polling mechanism between master and slave(s)

– Point-to-point and point-to-multipoint

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Packet Types

Controlpackets

Data/voicepackets

ID*NullPollFHSDM1

Voice data

HV1HV2HV3DV

DM1DM3DM5

DH1DH3DH5

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Packet Format

72 bits 54 bits 0 - 2744 bitsAccess code

Header Payload

DataVoice CRC

No CRCNo retries

625 µs

master

slave

header

ARQ

FEC (optional) FEC (optional)

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Packet Header

• Addressing (3)• Packet type (4)• Flow control (1)• 1-bit ARQ (1)• Sequencing (1)• HEC (8)

Access code

Header Payload

54 bits

Purpose

Encode with 1/3 FEC to get 54 bits

Broadcast packets are not ACKed

For filtering retransmitted packets

18 bitstotal

ss

m

s

16 packet types (some unused)

Max 7 active slaves

Verify header integrity

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Voice Packets (HV1, HV2, HV3)

Access code Header

Payload

72 bits 54 bits 240 bits

30 bytes

= 366 bits

10 bytes

+ 2/3 FEC

+ 1/3 FEC

20 bytes

30 bytesHV3

HV2

HV1

3.75ms (HV3)2.5ms (HV2)

1.25ms (HV1)

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Data rate calculation: DM1 and DH1

Payload

Accesscode Header

72 bits 54 bits 240 bits

30 bytes

= 366 bits

2/3 FEC

1 17 2DM1

1 27 2DH1

625 µs

625 µs

1 2

Dir

Size Freq Rate

17 1600/2 108.8

17 108.8

27 172.8

27 172.8

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Data rate calculation: DM3 and DH3

Payload

Access code

Header

72 bits

54 bits

1500 bits

187 bytes

= 1626 bits

2/3 FEC

2 121 2DM3

2 183 2DH3

1875 µs

1875 µs

Dir

Size Freq Rate

121 1600/4 387.2

17 54.4

183 585.6

27 86.4

1 2 3 4

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Data rate calculation: DM5 and DH5

Payload

AccessCode Header

72 bits

54 bits

2744 bits

343 bytes

= 2870 bits

2/3 FEC

2 224 2DM5

2 339 2DH5

3125 µs

3125 µs 625 µs

1 2 3 4 5 6

Dir

Size Freq Rate

224 1600/6 477.8

17 36.3

339 723.2

27 57.6

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ACL

SCO

Summary of Bluetooth Packet Types

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Bluetooth v2.0 Enhanced Data Rate (EDR)

• EDR achieves higher data throughput by using Phase Shift Keying (PSK) modulation, instead of Gaussian Frequency Shift Keying (GFSK) modulation.

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Bluetooth Physical link

• Point to point link– master - slave relationship– radios can function as masters or slaves m s

ss

m

s

• Piconet– Master can connect to 7 slaves– Each piconet has max capacity =1 Mbps

– hopping pattern is determined by the master

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Piconet capacity

One ACL link (432 kbps symmetric or 721/56 kbps asymetric)

or

Three simultaneous SCO links (64 kbps)

or

A combination of voice/dataM1

S1

S2

S4

S3

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Piconet Management

• Attach and detach slaves• Master-slave switch• Establishing SCO links• Handling of low power modes ( Sniff, Hold, Park)

req

response

Paging

Master

Slaves

s

m

s

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Connection Setup

• Inquiry - scan protocol– to learn about the clock offset and

device address of other nodes in proximity

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Baseband: Connection state

• Active mode: – Bluetooth unit listens for each master transmission. – Slaves not addressed can sleep through a transmission. – Periodic master transmissions used for sync.

• Sniff mode– Unit does not listen to every master transmission. – Master polls such slaves in specified sniff slots. – For ACL mode only.

• Hold mode– Master and slave agree on a time duration for which the slave is not polled. – The physical link is only active during slots that are reserved for the

operation of the synchronous link types SCO.

• Park mode– Slave gives up AM_ADDR. – Listens periodically for a beacon transmission to synchronize and uses

PM_ADDR/AR_ADDR for unparking.

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Low power mode (Sniff)

Master

Slave

Sniff period

Sniff offset

Sniff duration

• Traffic reduced to periodic sniff slots

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Low power mode (hold)

Slave

Hold duration

Hold offset

Master

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Low power mode (Park)

Master

Slave

Beacon interval

Beacon instant

• Power saving + keep more than 7 slaves in a piconet• Give up active member address, yet maintain

synchronization• Communication via broadcast LMP messages

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Piconet formation

Master

Active Slave

Parked Slave

Standby

• Page - scan protocol– to establish links with nodes

in proximity

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Intra-piconet communication

The master controls all traffic on the piconet

SCO link - reservation

The master allocates capacity for SCO links by reserving slots in pairs.

ACL link – polling scheme

The slave transmits in the slave-to-master slot only when it has been addressed by its MAC address in the previous master-to-slave slot. Therefore no collisions.

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Piconet MAC protocol : Polling

m

s1

s2

625 sec

f1 f2 f3 f4

1600 hops/sec

f5 f6

FH/TDD

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Multi slot packets

m

s1

s2

625 µsec

f1 f4 f5 f6

FH/TDD

Data rate depends on type of packet

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Physical Link Types

m

s1

s2

SCO SCO SCO

Synchronous Connection Oriented (SCO) Link slot reservation at fixed intervals

• Asynchronous Connection-less (ACL) Link– Polling access method

SCO SCO SCOACL ACL ACLACL ACL ACL

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Piconet capacity

One ACL link (432 kbps symmetric or 721/56 kbps asymetric)

or

Three simultaneous SCO links (64 kbps)

or

A combination of voice/data

M1

S1

S2

S4

S3

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Baseband: Summary

• TDD, frequency hopping physical layer• Device inquiry and paging• Two types of links: SCO and ACL links• Multiple packet types (multiple data rates with

and without FEC)

Baseband Baseband

L2CAPL2CAPLMPLMP

Physical

Data link

Device 2Device 1

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Networking

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Addressing

• Bluetooth device address (BD_ADDR)– 48 bit IEEE MAC address

• Active Member address (AM_ADDR)– 3 bits active slave address

– all zero broadcast address

• Parked Member address (PM_ADDR)– 8 bit parked slave address

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Why Scatternets

A group of overlapping piconets is called a scatternet

Users in a piconet share a 1 Mbps channel – individual throughput decreases drastically as more units are added

The aggregate and individual throughput of users in a scatternet is much greater than when each user participates on the same piconet

Collisions do occur when 2 piconets use the same 1 MHz hop channel simultaneously. As the number of piconets increases, the performance degrades gracefully

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Inter-piconet communication

A unit may particpate in more than one piconet on a TDM basis.

To participate on a piconet it needs the master’s identity and the clock offset.

While leaving the piconet it informs the master

The master can also multiplex as slave on another piconet. But all traffic in its piconet will suspended in its absence.

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Inter piconet communication

Cell phone Cordlessheadset

Cordless

headset

Cell phone

Cordlessheadset

Cell phone

mouse

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Scatternet

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Scatternet, scenario 2

How to schedule presence in two piconets?

Forwarding delay ?

Missed traffic?

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Bluetooth Scatternets

• Scatternet Formation Problem– Assignment of roles to devices

(Master / Slave / Bridge)– Independent devices, no prior

knowledge → distributed

– Formation time should be reasonable.– Assumption: all devices within

transmission range of each other.

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Piconet interconnection

6

5

34

7

4

51

28

3

12

923

35

42

9

15

14

1

32

10 45

8

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Bluetooth Scatternets

• Properties desired– Reachability (basic)– Number of piconets (minimize)– Network diameter (minimize)– Degree (minimize; bounded)– Number of bridge nodes (minimize)– Number of roles (minimize)

• Various Trade-offs

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Protocol Architecture

• Radio:– interface, frequency hopping, modulation, transmit power

• Baseband:– connection establishment in a piconet, addressing, packet format,

timing, power control

• Link Management Protocol (LMP):– link setup, authentication, packet size

• Logical Link Control and Adaptation Protocol (L2CAP):– adapts upper-layer protocols to baseband, connectionless service,

connection-oriented service

• Service Discovery Protocol (SDP):– device info (service, characteristic), service query

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How some companies view Bluetooth's future

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PPP

Protocols and Usage Models

RFCOMM

TCP/IP

Baseband

L2CAP

OBEX

IrMC

TCS-BIN

Audio

SyncDial-up

net.

Usage Models

FileTransfer

AT-commands

Fax HeadsetLAN

AccessCordlessPhone

SDP

LMP

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SONY / CASIO

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HP

• Print data from network:– maps, emails, web pages, …

• Print phone book & other phone data

• Print directly from camera

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Siemens

• Cable replacement

• Home Access Point

• Home Control

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CASIO

• Intelligent home:– Door lock, Light, Audio/Video, Electronic equipment, Automatic

synchronisation, ...

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Research on Bluetooth

• Coexistence with other wireless technologies• Opportunistic Bluetooth overlay networks• Cross layer integration• ???